1. Peel the wrapping, if any, from ham; place ham on a rack in a large, shallow, baking pan. (Do not add water or cover pan.)
2. Bake in slow oven (325°) 1 1/2 hours; remove from oven.
3. Using a sharp, thin-blade knife, make parallel cuts, 1/2-inch deep and 1/4 inch apart, in top of ham. Insert half an orange slice in each of the cuts.
4. Blend the pineapple-orange-juice concentrate and honey in a small bowl; brush part over the ham and oranges.
5. Continue baking, brushing several times with remaining juice-honey mixture, 30 minutes, or until richly glazed. Remove to a heated, large, serving platter. Slice ham 1/4-inch thick.